This patent describes Antoine Audouard’s Le Crack design of racing derailleur. Unlike his earlier design (French patent # 425,800), the Audouard Le Crack was a conventional mechanism in that the derailleur moved laterally the the freewheel cogs did not.

The derailleur itself was a somewhat crude affair, moved sideways by a crude lever. However this basic design allowed top and bottom normal options - and the top normal option pre-dated the rather similar Simplex bell-crank design by nearly a decade.

• Publisher: L’Institut national de la propriété industrielle
• Inventor: Jean-Antoine Audouard
• Country: France
• Date: French application January 1924
• Derailleur brands: Audouard
• Derailleurs: Audouard Le Crack